This paper discusses the geochemical characteristics of the interstitial water of the Bohai Gulf, where the main salt contents (K+, Na+, Ca++ Mg++, Cl-, HCO3-, SO4-) in 55 sedimentary layers of 13 cores (3-4 m in length) and those of bottom seawater have been determined and the exchange capacity and exchange cations (K+, Na+, Ca++, Mg++) of the layers analysed (see Fig.1).